A transformer is a key component for a wild variety of electronic devices. The most pressing problems facing the industry will be the safety issue, especially when the design trend of electronic devices tends to reduce the device size and cost. As a matter of fact, the components inside various electronic devices are placed in high density nowadays.
In general, a conventional transformer would comprise a winding coil, a magnetic core, and a bobbin mounted by the winding coil. As shown in FIGS. 1 and 2, they are an exploded view and an assembled view of a conventional transformer. The transformer 10 is constructed by the combination of the magnetic core 11 and the bobbin 31 which is mounted by the winding coil 21. As illustrated, the construction to assemble the magnetic core 11 with the bobbin 31 is done through the combination between a central post 111 of the magnetic core 11 and a perforation channel 313 of the bobbin 31. The perforation channel 313 provides room to accommodate the central post 111.
As shown, a primary input port 311 and a secondary output port 417 are both placed on the bobbin 31 and extended outward from two opposite sides of the bobbin 31. The assembled transformer 10 appears just a bit larger than the magnetic core 11 since the bobbin 31 extend a bit outward for receiving power by the primary input port 311 and supplying power by the secondary output port 417. However, the assembled transformer 10 and the magnetic core 11 are tempted to be designed of almost the same size by the recent trend. This design is to spare more room for an electronic device to accommodate more components within a limited space under the high density condition.
On the other hand, the conventional transformer as illustrated in FIGS. 1 and 2 also suggests a safety issue arising from the same construction, since the exposed portion of the magnetic core 11 open to the outside space is so close to other components which are disposed nearby (not shown). In other words, this would certainly cause extra efforts to improve and verify the insulating of the transformer 10 so as to prevent from any serious electrical safety issue. As well known in the art, to seal the exposed portion of the magnetic core 11 by an insulating tape or an adhesive tape (not shown) is the most common way to solve the foregoing problem. It is a simple idea to separate two conductive parts from each other by attaching a sticky tape to either one or both of them. Nevertheless, the insulating results can vary and be unstable. For example, it depends upon the material of the tape, the finishing jobs in fabricating, and the condition in use.
Accordingly, several disadvantages emerge. While in fabricating, it is easily to be understood that such transformers would require paying more attention to the security of the insulating tape. Especially, the exposed portion is quite huge and the insulating tape is required to be attached and secured by hand in normal cases. Even though the tape has been attached precisely right to the required portion, the security of the tape can fail at any time resulting from inadvertently move or touch conducted by the worker during the assembly. Besides, the security of the insulting tape may come to be unstable over time. Following inspections are thus crucial and necessary all the time. Also, it appears that the conventional transformers may not be suitable for the use of the electronic devices which are under the high density design. Likewise, the traditional way has shown that more risks might arise while such transformers are for the use with a portable electronic device. As known, it is the nature of a portable device that any kind of unexpected collisions against the device can be reasonably expected in advance. The collision accidents may cause the components inside becoming, for example, loose or distortion, and may directly result in a breaking of the insulating which may lead to serious electrical safety issues.
Apparently, a transformer which is of simple construction and capable to meet the needs for increasing more safety in use and reducing costs in fabricating are in demand.